Device for cutting screw-threads.



T. SHEHAN.

DEVICE FOR CUTTING SCREW THREADS,

APPLICATION FILED JUNE 21.1917.

1,265,821; Patented M8 14, 1918.

3 SHEETS-SHEET I.

T. SHEHAN.

DEVICE FOR CUTTING SCREW THREADS.

APPLICATION FILED JUNE 21, I9I7.

1 ,265,821 Patented May 14, 1918.

3 SHEETS-SHEET 2.

T. SHEHAN DEVICE FOR CUTTING SCREW THREADS.

APPLICATION FILED JUNE 21, I917. I 7 1,265,821. Patented May 14, 1918.

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2% L/ g [nyengrli THOMAS SHEHAN, OF CLEVELAND, OHIO.

DEVICE FOR CUTTING SCREW-THREADS.

Application filed June 21, 1917.

To (ZZZ whom it may concern Be it known that I, THOMAS SHEHAN, a citizen of the United States of America, residing atCleveland, in the county of Guyahoga and State of Ohio, having invented certain new and useful Improvements in Devices for Cutting ScrewThreads; and I hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it pertains to make and use the same.

This invention relates to improvements in devices for cutting screw-threads, and pertains more especially to a screw-cutter or device for cutting external screw-threads and comprising a cutter-head which has a centrally located bore extending endwise or longitudinally of the cutter-head and is provided in its forward portion with radially arranged g'uideways which are spaced circumferentially of said bore and engaged by cutters adapted for cutting screw-threads.

One object of this invention is to provide a screw-thread-cutting device of the character indicated with improved simple, durable and reliable means for shifting or adjusting the cutters simultaneously.

Another object is to provide improved means whereby the cutters, upon having completed their cutting operation on the object to be screw-threaded, are simultaneously and correspondingly withdrawn from the work.

Another object is to provide means where by the cutters, when they 'are in position for cutting a screw-thread, can be readily simultaneously and correspondingly readjusted for making a deeper or shallower cut.

Another object is to facilitate the making and assembling of the component parts of my improved screw-thread-cutting device and to render said device reliable in its ope 'ation and not liable to get out of order.

With these objects in view, and to attain any other object hereinafter appearing, this invention consists in certain features of construction, and combinations and relative arrangement of parts, hereinafter described in this specification, pointed out in the claims, and illustrated in the accompanying drawings.

In said drawings, Figure 1 is a side view of a portion of a machine provided with my improved device for cutting screw-threads, and shows the object or work which is to be Specification of Letters Patent.

an upright standard a from Patented May let, 1918.

Serial No. 178,073. 7

externally screw-threaded by said device. Fig. 2 is a forward end view of said screwthread-cutting device. Fig. 3 is a vertical section taken transversely through the cutter-head along the line 33, Fig. 1, looking rearwardly. Fig. 4c is a central longitudinal vertical section taken along the line M, Fig. 3, looking in the direction indicated by the arrow. Fig. 5 is a transverse vertical section taken along the line 55, Fig. 4:, looking rearwardly. Fig. 6 is a transverse vertical section taken along the line 6-6,

ig. at, looking forwardly. Fig. 7 is a transverse vertical section taken along the line 77, Fig. 4, looking rearwardly. Fig. 8 is a longitudinal section taken along the line 88, Fig. 3, looking in the direction indicat-ed by the arrow. Fig. 9 is a section, in detail, taken along the line 9 9, Fig. 5. 10 is a longitudinal section taken along the line 1010, Fig. 3, looking inthe direction indicated by the arrow. Fig. 11 is a vertical section, in detail, taken along the line l11l, Fig. 3. Fig. 12 is a transverse vertical section taken along the line 12l2, Fig. 10, looking forwardly. Fig. 13 is a forward end view of a cutter-operating shaft detached and shows the associated bushing on the arm of said shaft. Fig. 14 is a left-hand side view relative to Fig. 13. Fig. 15 is a forward edge View of a cutter detached. Fig. 16 is a right-hand side elevation relative to Fig. 15. Portions are broken away in said drawings to reduce the size of the drawin s.

xeferring to Fig. 1 of the drawings A indicates the bed of a machine provided with which my improved screwthreacl-cutting device is supported. Said device for cutting screwthreads comprises a circular stock having a circular stationary inner portion or body B. Said screw-thread-cutting device also comprises a cutter-head having a circular portion or body C interposed between two parallel circular end-plates 18 and 19 which (see Fig. 4) form the forward end face and rear end face respectively of the cutter-head, and D indicates the cutters of the cutter: head. A workfeeding head E (see Fig. l) is shown engaging a slideway 20 formed in the bed A, and said slideway is arranged as required to enable said head to be moved toward and from the screw-thread-cutting device. F indicates a horizontally arranged spindle which. has bearing in the head E and tweenthe'ends thereof with a recess Z which extends transversely of and horizontally through; said cutter and is engaged by a tooth, 72, formedon a horizontally arranged shaft H which extends transversely of the cutter and between the end plates 18 and 19 of the cutter-head andv consequently: endwise. of the cutter-head. Said shaft has hearing I in the cutter-headand preferably extends through the rear end plate 19 of the cutter-head. Preferably the aforesaid tooth is formed byrthe partition 01: wall ,between two recesses 43 which are formed in the. forward end-portion of said shaft, and said recesses are spaced circiunferentially of the shaft and extend rearwardly from the forward'extremity of the shaft=a distance measuring t least-as much as the width of the associated cutter; Obviously by the forination of saidtooth by the wall between said recesses the, forward end-portion or toothed portion ofsaid shaft is not any larger in diameterthan the remainder of the shaftand does notinterfere with the insertionofsaid shaftinto the. cutter-head from the rearend of the bodyof thecutter-head. It will alsobe observed'that said a tooth pushes laterally against the one or the other side wall of the engaging recesszl, in the associated cutter,and consequently said jcutter isactuated inwardly or-outwardly, according as the shaft is rotated in-the one or the other e direction Means .for rotating the cutter-actuating shafts H simultaneously and in unison are provided and comprise a ringv Irotatably mounted on. the rear end-portion of the body C of the cutter-head between the shoulder 38am} the rear end plate 19 of the cutterhead, and said plateis shown overlapping the rear end faceof'said ring. The shafts Hand the ring I have their axes parallel, and eachshaft H hasits rear end-portion (see Figs. and 12) provided, nextforward of the rear endpla-te of the cutterhead, with an arm which projects outwardly into a recess 46 formed in said ring at the internal surfaceof the ring and extending forwardly from therear extremity of the ring. Said arm is loosely embraced bya bushing 47 which is U-shaped and externally circular. in cross-section and has bearingin t-hering I and hasits'axis ,parallelvwith the axis of the ring. By the construction hereinbefore described it will be observed that the ring .I is confined next forward ofthe rear end plate 19 of the cutter-head endwise of. the cutter-head,- that said ring is provided internally with recesses spaced circumferentially of the cutterhead, that the hereinbefore mentioned. bushings engage said recesses and are rotatably 1no1.u 1tedinsaid ring and flush 'at (their rear end faces with the rear end face ofsaid ring,

as that the shafts are arrangedwithia tor-head adjacent said-bushings and have their arms45 next forward of said plate of the cutter-head and that said plate overlaps said arms and therear end faces of the bushings and therefore constitutes means for preventing rearward displacement of the bushings and shafts. The operative connection between each, shaft H and the ring I is formed by the arm 45 of said shaft and the adjacent bushing 47, and the relative arrangement ofthe parts is such that said arm extends into said bushing in either extreme positionofthe cutter associated with said shaft. Obviously all of the shafts are simultaneously operated during the rotation of the ring I; and as the arms ofall of the shafts project outwardlyinto said ring said shafts are rotated in the same direction during the rotation of the said ringint one direction, and the shafts are rotated in. the one direction or the other according as said ring is rotated in the one or the other direction. The relative arrangement of each shaft and the cutter operatively connected or associated with said shaft corresponds with therela-tive arrangement of each other cutter and associated shaftso that all of the cutters are simultaneously and correspondingly actuated endwise outwardlyor inwardly according as the ring I is rotated in the one or the other direction. Itwill be observed that in my improved operative connection between the ring I and the shafts H friction is reduced to a minimum, that the component parts of the operative connection between said ringand the cutters are readily assembled, that the bushings are readilyrenewable and that the construction is simple and durable. The ring Iis provided with a handle 48 for rotating the ring, and the body O ofthe cutter-head is cut away, as at 49, Fig. 12, adjacent the arm 45 of eachhshaft H to permit'therequired limited rotation of said shaft. Of course, the shafts H preferably correspond in dimensions and are spaced equidistantly from and equidistantly circumferentially of the central bore 27 in the cutter,head., A shaft H and the bushings? on the arm of said shaft are shown detached in. Figs. 13 and 14. The cutters are shown in {their inner position ready for the reception between them of the work, such, for instance, as a rod, screw-blank or other object 23 upon which screw-threads areto be cut by the cutters. A cutter D is shown detached in Figs. 15 and 16. In assembling the parts obviously the shafts H, upon mounting the bushings 47 on the arms of the shafts, are inserted into place from the rear end of the body of the cutter-head after the application of the ring I and preparatory to the applicationof the rear end plate 19 of the cutter-head.

The steelsv tees-Figs 1 e,- ,7, sand 10) also comprises a circular collar which is loosely mounted on and adjustable circumterentially of the body B oi the stock. The collar 50 is concentric relative to the ring I, and constitutes the outer portion of the stock. The body B of the stool: is provided with an external annular recess 51 which extends circumterentially of said body and is concentric relative to the collar 50. lhe pins 31 of said body B extend into and transversely of the recess 51 and have their recessengaging portions forming two shoulders 52 which are arranged between the side walls and extend t 'ansversely of said recess and face laterally of the stock in the same direction and are spaced CllCllllliiGlQlP tially of said body. One of the shoulders 52 is engaged by the inner end of one screw of a pair of parallel screws K. and the other of said shoulders is engaged by the inner end of the other of the said screws; Said screws engage and extend through correspondingly arranged and correspondingly screw-threaded holes 53 formed in the col-- lar 50 and cooperate with the shoulders 52 in constituting means for securing the collar in the desired adjustment circumferentially of the body B of the stock, and obviously said collar is readjusted circumterentially of said body by the required manipulation of said screws. By the construction hereinbefore described it will be observed that the screws K are threaded into the collar 50 at one side of the stool: and opposite the shoulders 52 and extend into the recess 51 in the body B of the stock and form abutments for said shoulders. Another screw L is threaded into the collar 50 at the opposite side of the stool: and extends into said recess 51, and the width of said recess is such relative to the diameter of the recess-engaging portions or the screws h: and L that opposite side walls of said recess are arranged in close proximity to opposite sides respectively of said screws and cooperate with said screws in constituting meanstor preventing displacement of said collar endwise oi the body of the stock.

The collar 50 (see Figs, l, 6, 8 and 10) is provided at its forward end with a forwardly projecting annular flange 55 which is concentric relative to said collar and consequently concentric relative to the ring I and extends circumferentially or and loosely embraces the rear end plate 19 of the cutterhead.

Said flange 55 is provided at its forward end face with several holes 56 spaced equidistantly circumferentially of the plate 1.9, and consequently circumterentially oi? the body of the stock. Each hole 56 is engaged by a horizontally arranged pin 57 with which the ring l is provided. That is, said ring carries as many pins 57 as there are holes 56 in the flange 55 ot' the collar 50,

and said pins are parallel with the axis of the ring. Preferably said ring (see Figs. t and 5) is provided at its forward end face with an annular recess 58 arranged concentrically relative to said ring, and said ring is shown provided at its rear end with a rearwardly projecting annular flange 59 loosely embracing the flange 55 of the collar 50. The pins 57 extend from within the recess 58 rearwardly and beyond the rear end of the ring I and into the holes 56 in the tlange 55 olthe collar 50 and are removable from said collar as will hereinafter appear. The pins 5'? are rigid with the ring I and cooperate with the flange 55 of the collar 50 of the stock in locking said ring to the stock against rotation on the body C of the cutter-head, but obviously said ring is rendered free to rotate on the cutter-head upon the movement of said ring with the cutter-head far enough forwardly from the stock to render said pins inoperative by removing or disengaging them from the holes56 in said flange 55. @bviously a rotation of the ring I on the cutter-head in the direction indicated by the arrow 60 in Fig. 5, upon the forward movement of the cutter-head from the stock the extent required to unlock said ring from the stock, efiects the rotation of the shafts H in the direction required to result in the outward actuation of the cutters D from their inner and thread-cutting position into their outer and work-releasing position. Suitably applied springs M, arranged within the recess 58 in the ring I and spaced and extending circumferentially of the cutter-head and normally under tension, act to rotate said ring in the direction indicated by the arrow 60, Fig. 5. Preterably to the forward end of each pin 57 is attached one end of a. spring M which extends from said pin circumferentially of the cutter-head in the direction indicated by said arrow 60 and is attached at its opposite end by a screw 61 (see Figs. 5 and 9) to thebody C of the cutter-head. it will be observed therefore that the springs M constitute resilient means acting to rotate the ring I in the direction required to withdraw the cutters from their operative position, that my improved screw-thread-cutting device comprises mcans whereby said ring is locked against rotation, and said locking means is adapted to be rendered inoperative by a shitting of said ring with the cutter-head forwardly from the stack the required extent.

The outer circumferential surface of the ring I is provided adj acent the forward end of the ring (see Fig. 1) with a line or mark 62 with cooperates with a scale 63 formed on the adjacent portion of the outer circumferential surface of thebody G of the cuttor-head in indicating the adjustment or position of the cutters.

it will also be observed that 65 in Fig. 1

loo

indicates a lug formed on the bed A and arranged to limit movement of the work-feeding head E toward my improved screwthread-cutting device. The relative arrangement of the parts is such that, when the work 23 has been fed by said work-feeding head into position to be operated on by the cutters D and rotated while being 0perated on by said cutters, the stop will arrest the endwise movement of the work near the end of the operation on the work by said cutters, whereupon the rotating work, having said movement thereof arrested, will pull the connected cutter-head, and consequently the ring I, forwardly toward the workfeeding head, and the relative arrangement of the parts is furthermore such that when the cutters have completed their thread cutting operation on the work the ring I shall have been shifted forwardly far enough to have removed its pins 57 from the holes 56 in the collar 50 of the stock so as to release or unlock said ring from the stock and render said ring subject to the action of the. springs M and permit said springs to rotate said ring in the direction required to efiect the actuation of the cutters outwardly and thereby cause the cutters to withdraw from and release the work.

What 1 claim is z- 1. In a device for cutting screw-threads, a cutter-head provided in its forward portion with guideways arranged substantially radially of the cutter-head, cutters engaging the guideways and each provided in one side thereof with a recess extending transversely of the respective cutter, a shaft associated with each cutter and extending transversely and rearwardly of the cutter and having bearing in the cutter-head, and a ring rotatably mounted on the cutter-head and operatively connected with the shafts, each shaft being provided in its forward end-portion with two recesses which extend longitudinally and are spaced cireumferentially of the shaft and having the wall or partition between said recesses forming a tooth which engages the recess in the cutter associated with said shaft, and the cutters being adapted to be shifted outwardly or inwardly according as the aforesaid ring is rotated in the one or the other direction.

2. In a screw-thread-cutting device, a cutter-head provided with guideways arranged substantially radially of the cutterhead, cutters engaging the guideways and each providedin one side thereof with a recess extending transversely of and through the respective cutter, a shaft associated with each cutter and extending transversely and rearwardly of the cutter and having bearing in the cutter-head, and a ring rotatably mounted on the cutter-head and operatively connected with the shafts, each shaft being provided in its forward end-portion with two recesses which are spaced circumferen tially of the shaft and having the partition between said recesses forming a tooth which engages the recess in the cutter associated with said shaft, the cutters being adapted to be simultaneously shifted outwardly or inwardly according as the aforesaid ring is rotated in the one or the other direction, and the aforesaid recess in each shaft extending rearwardly from the forward extremity of the shaft :1 distance measuring at least as much as the width of the cutter associated with said shaft.

3. In a screw-thread-cutting device, a cutterhead provided with guideways which are arranged substantially radially of the cutterhead and comprising a body and two end plates arranged to form the forward end face and rear end face respectively of the cutter-head and reinovably secured to said body, cutters engaging the guideways, shafts operatively connected with the cutters and extending between the end plates of the cutter-head and into the rear end plate of the cutter-head, and a ring rotatably mounted on the body of the cutter-head and operatively connected with the shafts, the cutters being adapted to be simultaneously shifted outwardly or inwardly according as said ring is rotated in the one or the other direction, the shafts having bearing in the cutterhead, and the aforesaid rear end plate overlapping the rear end face of said ring.

4. In a screw-thread-cutting device, a cutter-head provided with guideways arranged substantially radially of the cutterhead, cutters engaging the guideways, a rin rotatably mounted on the cutter-head and provided internally with recesses spaced circumferentially of the cutter-head, bushings engaging said recesses and rotatably mounted in said ring, and shafts arranged within the cutter-head adjacent said bushings and extending endwise of and having bearing in the cutter-head, said shafts being operatively connected with the cutters and provided with arms extending into and be ing loose relativeto said bushings,'the cutters being adapted to be simultaneously shifted outwardly or inwardly according as the aforesaid ring is rotated in one or the other direction, the arms of the shafts projecting into the bushings in, either extreme position of the cutters, and the bushings, the shafts and the ring having their arms parallel.

5. In a screw-thread-cutting device, a cutter-head provided in its forward portion with guideways which are arranged substantially radially of the cutter-head 21I1Cl'00111- prising a body having an external rearwardly facing shoulder which is spaced forwardly from the rear extremity of the cutter-head and also comprising a plate arranged to form the rear end face of the cutter-head, cutters engaging the gu'deways, a ring rotatably inoiuued on the cutter-head between said plate and th Urns-aid shoulder and provided internally with recesses spaced circainterentially or the cutter'head and er:- tending forwardly from the rear end face ot the ring, bushin s engaging said recesses and rotatably mount d in said ring and flush at their rear end faces with the rear end face of the ring, and sha'l'ts extending endwise 0t and having bearing in the cutterhead, said snat'ts being operatively connected with the cutters and provided at their rear ends with arn extending into and being loose relative to said bushings, the cutters being adapted to be intuitaneously shifted utwardly or hurt lly according as the aforesaid ring is rotated in the one or the other direction, and the aforesaid plate overlapping the rear end faces of the bushings.

6. In a screW-tliread-cutting device, a cut tor-head provided in its lorW-ard portion with guideways which are arranged substantially radially of the cutter-h ad and comprising a body and an end plate arranged to form the rear end face of the cutter-head, cutters engaging the guideways, ring rotatably niou ted on the aforesaid body and provided internally with recesses spaced circuinterentially of the cutter-head and extending forwardly "from the rear end of the ring, bushings engaging said recesses and rotatably mounted in the ring, and shai'ts extending endwise of and having bearing in the cutter-head, said sh its being operatively connected with the cutters ant l providet next forward of the aforesaid plate with arms extending into and being loose relative to said bushings, the cutters being adapted to be sinniltaneously shiited outwardly or inwardly according as the aforesaid ring rotated in the one or the other direction, the arms the shafts projecting into the bushings in either extreme position of the cutters, th aforesaid plate overlapping the rear end race oi' said ring 1' end faces oi. the bushings, and

and the rea the bi shings the ring and the shatts ha ing their axes parallel.

7. in a screW-thread-cutting device, a. stock, a cutter-head forward of: and supported and shit'table forwardly from the stock and provided with guideways arranged substantially radially ot the cutterhead, cutters engaging the guideways, a ring rotatably mounted on the cutter-head, shafts extending endir se of and having bearing in the cutter-head and being operatirely connected with the cutters and "with the aforesaid ring, resilient inc-ans arcing to rotate said ring in the direction required to withdraw the cutters from their operative position, and 111521113 (hereby said is locked against rotation to the stock, the cutters being adapted to be simultaneously shifted outwardly or inwardly according as said ring is shifted in the one or the other direction, and the aforesaid locking means being adapted to be rendered inoperative by the required shitting of the ring with the outtenhead 'forvardly from the stock.

8. In a screW-thread-cutting device, a Holt, a cutter-head forward of and supported and shittable forwardly from the stock and provided with guideways arranged substantially radially of the cutterhead, cutters engaging the guideways, a ring rotatably mounted. on the cutter-head, shafts extending endwise of and having bearing in the cutter-head and operatiyely connected with the cutters and With said ring and having their axes parallel with the axis of the rin yspiral springs acting to 1'0- tate said ring in the direction required to Withdraw the cutters from their operative position, and means whereby said ring is locked against rotation, said locking means being adapted to be rendered inoperative by a shifting of the ring With the cutter-dread forwardly the required extentfrom the stock, the cutters being adapted to be simultaneously shifted outwardly or inwardly according as said ring is rotated in the one or the other direction, said ring being provided at its forward end with an annular recess extending circuniferentially of the cutter-head, and the aforesaid springs being arranged Within said recess and circumferentially of the cuttenhead and attached at one end to the cutter-head and at the other end to the ring.

a. in screwthread-cutting device, a stool; having a circular body and comprising a collar wanted on and adjustable circuini erentially of said body, means for se curing said collar in the desired adjustment, a cuttenhead forward of and supported and shittaole forwardly from the aforesaid body oi the stool: and provided in its forward portion with guideWay-s arranged substantiall v radially of the cutter-head, cutters en oa 'in c tne guideways, a ring rotatably mounted on the cutter-head and confined 1 'se of the cutterdiead, shafts extending enduise or and having bearing in the cutterhead and operatiyely connected with the cutters and with said ring, resilient means V acting to rotate said ring in the direction required to Withdraw the cutters from their operative position, and means normally loc ring said ring to the aforesaid collar, said locking means being adapted to be rendered inoperative by a shifting of said ring with the cutter-head forwardly from the stock the required extent.

ltlln screw-thread-cutting device, a stock having a circular body and comprising a collar mounted on and adjustable circuinerentially of said body, means for securing i: said collar in the desired adjustment, a cutter-head forward of and supported and shiftable forwardly from the aforesaid body of the stock and provided in its forward portion with guideways arranged substantially radially'of the cutter-head, cutters engaging the guideways, a ring rotatably mounted on the cutter-head and confined endwise of the cutter-head, shafts extending endwise of and having bearing in the cutterhead and operatively connected with the cutters and with the aforesaid ring, and resilient means acting to rotate said ring in the direction required to withdraw the cutters from their operative position, said ring and the aforesaid collar being provided the one with pins and the other with holes normally engaged by said pins so as to lock said ring to said collar, and said pins being disengaged from said holes by a shifting of said ring with the cutter-head forwardly the required extent.

11. In a screw-thread-cutting device, a stock having a body and comprising a cOllar mounted on and adjustable circumferentially of said body, means for securing said collar in the desired adjustment, a cutterhead forward of and supported and shiftable forwardly from said body and provided in its forward portion with guideways arranged substantially radially of the cutterhead, cutters engaging the guideways, a ring rotatably mounted on and being carried by the cutter-head, shafts extending endwise of and having bearing in the cutter-head and operatively connected with the cutters and with said ring, resilient means acting to rotate said ring in the direction required to withdraw the cutters from their operative position, and pins carried by said ring and extending into the aforesaid collar and normally locking said ring to said collar and being adapted to be withdrawn from said collar by movement of the cuttenhead forwardly from the stock the required extent.

12. In a screw-thread-cutting device, a stock having a body and comprising a collar mounted on and adjustable circumferentially of said body, means for securing said collar in the desired adjustment, a cutterhead forward of and supported and shiftable forwardly from said body and provided in its forward portion with gnideways arranged substantially radially of the cutterhead, cutters engaging the guideways, a ring rotatably mounted on and carried by the cutter-head and operatively connected with the cutters and provided at its forward end face with a recess extending circumferentially of the cuttenh'ead, pins carried by said ring and spaced circumferentially of the cutter-head and normally projecting into the aforesaid collar and locking said ring to said collar and adapted to be withdrawn from said collar by movement of the cutter-head forwardly from the stock the required extent, and spiral springs arranged within the aforesaid recess and circumferentially of the cutter-head, each spring being attached at one end to one of the aforesaid pins and at its other end to the cutter-head and acting to rotate the aforesaid ring in the direction required to withdraw the cutters from their operative position.

13. In a screw-thread-cutting device, the combination, with a stock having a circular body which is provided with an external circumferentially extending recess and com prising a collar mounted on and adjustable circumferentially of said body, a cutter-head forward of and supported and movable forwardly from the stock and having substantially radially arranged guideways, a ring rotatably mounted on and carried by the cutter-head, cutters operatively connected with said ring and engaging the aforesaid guideways, resilient means acting to rotate said ring in the direction required to withdraw the cutters from their operative position, and locking means normally locking said ring to the aforesaid collar and adapted to be rendered inoperative by movement of the cutter-head. forwardly from the stock the required extent, and the body of the stock having two shoulders arranged between the side walls of the aforesaid recess and spaced eircumferentially of said body, of several screws threaded into the aforesaid collar and extending into said recess and spaced circumferentially of said body, two of said screws being arranged to cooperate with said shoulders in securing said collar in the desired circumferential adjustment, and the width of said recess being such relative to the diameter of the recessengaging portions of the screws that the side walls of said recess cooperate with the screws in preventing endwise displacement of said collar.

let. In a screw-thread-cutting device, a stock having a body and comprising a collar mounted on and adjustable circumferentially of said body, means for securing said collar in the desired circumferential adjustment, a cutter-head forward of and support ed and movable forwardly from the body of the stool: and having substantially radially arranged gnideways and comprising a plate which forms the rear end face of the cutterhead and is larger diametrically than the adjacent portion of the body of the cutterhead, resilient. means acting to retain the cutter-head in rearward and normal position, a ring rotatably mounted on the cutterhead next forward of the aforesaid. plate, cutters operatively connected with said ring and engaging the resaid guidewa s, and resilient means acting to rotate said ring in the direction required to withdraw the cutters from their operative position, the aforesaid collar having a flange loosely embracing and 1110113 whereof, E Sign "the forego- .ficadnon 1n the presence 01"" two w1t- 1101255 and 11 snia 3H1 some dise lgageu 1 a :1 the required moven'en fnrwarchy from 61a, stock.

" Gmnmissioner 0i Bea-tents may as obirainefi for 1;,e cents each, 1 

